climate crisis David Battisti

If You Thought This Summer’s Heat Waves Were Bad, Here’s Some Disturbing News

A new climate study has stark warnings about dangerous heat in the future.
Due to the climate crisis, it’ll get harder and harder to cool down in summer. [Apionid / CC BY-NC-ND 2.0]
By David Battisti, University of Washington

As global temperatures rise, people in the tropics, including places like India and Africa’s Sahel region, will likely face dangerously hot conditions almost daily by the end of the century – even as the world reduces its greenhouse gas emissions, a new study shows.

The mid-latitudes, including the U.S., will also face increasing risks. There, the number of dangerously hot days, marked by temperatures and humidity high enough to cause heat exhaustion, is projected to double by the 2050s and continue to rise.

In the study, scientists looked at population growth, economic development patterns, energy choices and climate models to project how heat index levels – the combination of heat and humidity – will change over time. The Conversation asked University of Washington atmospheric scientist David Battisti, a co-author of the study, published Aug. 25, 2022, to explain the findings and what they mean for humans around the world.

What does the new study tell us about heat waves in the future, and importantly the impact on people?

There are two sources of uncertainty when it comes to future temperature. One is how much carbon dioxide humans are going to emit – that depends on things like population, energy choices and how much the economy grows. The other is how much warming those greenhouse gas emissions will cause.

In both, scientists have a really good sense of the likelihood of various scenarios. For this study, we combined those estimates to get a likelihood in the future of having dangerous and life-threatening temperatures.

We looked at what these “dangerously high” and “extremely dangerous” levels on the heat index would mean for daily life in both the tropics and in the mid-latitudes.

“Dangerous” in this case refers to the likelihood of heat exhaustion. Heat exhaustion won’t kill you if you’re able to stop and slow down – it’s characterized by fatigue, nausea, a slowed heartbeat, possibly fainting. But you really can’t work under these conditions.

The heat index indicates when a person is likely to reach that threshold. The National Weather Service defines “dangerous” as a heat index of 103 F (39.4 C), and “extremely dangerous” as 125 F (51.7 C). If a person gets to “extremely dangerous” temperatures, that can lead to heat stroke. At that level, you have a few hours to get medical attention to cool your body down, or you die.

Illustration of human body listing symptoms of heat strike and heat exhaustion.
Signs of heat illness. elenabs via Getty Images

“Extremely dangerous” heat index conditions are almost unheard of today. They happen in a few locations near the Gulf of Oman, for example, for maybe a few days in a decade.

But the odds of the number of “dangerous” days are increasing as the planet warms. We’ll likely have about the same weather variability as today, but it’s all happening on top of a higher average temperature. So, the likelihood of extremely hot conditions increases.

What does your study show for each region?

In the mid-latitudes by 2050, we’ll see the number of dangerous heat days double in the most likely future scenario – even under modest greenhouse gas emissions that would meet the Paris climate agreement target of keeping warming under 2 C (3.6 F).

In the Southeastern U.S., the most likely scenario is that people will experience a month or two of dangerous heat days every year. The same is likely in parts of China, where some regions have been sweating through a summer 2022 heat wave for over two straight months.

We found that by the end of the century, most places in the mid-latitudes will see a three- to tenfold increase in the number of dangerous days.

In the tropics, such as parts of India, the heat index right now can exceed the dangerous level for a few weeks a year. It’s been like that for the past 20 to 30 years. By 2050, those conditions are likely to occur over several months each year, we found. And by the end of the century, many places will see those conditions most of the year.

What that means in practice is if you’re a rich country like the U.S., most people can afford or find air conditioning. But if you’re in the tropics, where about half the world’s population lives and poverty is higher, the heat is a more serious problem for a good part of the year. And a large percentage of people there work outside in agriculture.

Maps show study's projections
The average number of days with dangerous heat index levels in 1979-1998 and the study’s median projections for 2050 and 2100. Zeppetello, Raftery & Battisti, 2022

As we get toward the end of the century, we’ll start exceeding “extremely dangerous” conditions in several places, primarily in the tropics.

Northern India could see over a month per year in extremely dangerous conditions. Africa’s Sahel region, where poverty is widespread, could see a few weeks of extremely dangerous conditions per year.

Can humans adapt to what sounds like a dystopian future?

If you’re a rich country, you can build cooling facilities and generate electricity to run air conditioners – hopefully they won’t be powered with fossil fuels, which would further warm the planet.

If you’re a developing country, a very large fraction of people work outdoors in agriculture to earn money to buy food. There, if you think about it, there aren’t a lot of options.

Migrant workers in the U.S. also face more difficult conditions. A farm might be able to provide cooling facilities, but farmers’ margins are pretty small and migrant workers are often paid by volume, so when they aren’t picking, they aren’t paid.

Eventually, conditions will get to the point that more workers are overheating and dying.

Farm workers sit in an open-air truck with a tarp over the top for shade.
U.S. farmworkers take a break from picking melons on a July 2021 week when temperatures were expected to pass 110 F. AP Photo/Terry Chea

The heat will be a problem for crops, too. We expect most of the major grains to be less productive in the future because of heat stress. In the mid-latitudes right now, we’re close to optimal temperatures for growing grains. But as temperatures increase, grain yield goes down. In the tropics, that could be anywhere between a 10% to 15% reduction per degree Celsius increase. That’s a pretty big hit.

What can be done to avoid these risks?

Part of our work in this study was determining the odds that the world will actually meet the Paris agreement. We found that to be around 0.1%. Basically, it’s not going to happen.

By the end of the century, we found the most likely scenario is that the planet will see 5.4 F (3 C) of warming globally compared to pre-industrial times. Land warms faster than ocean, so that translates to about a 7 F (3.9 C) increase for places where we live, work and play – and you can get a sense of the future.

The faster renewable energy comes online and fossil fuel use is shut down, the better the chances of avoiding that.

David Battisti, Professor of Atmospheric Sciences, University of Washington

This article is republished from The Conversation under a Creative Commons license. Read the original article.

13 comments

  1. “the number of dangerously hot days, marked by temperatures and humidity high enough to cause heat exhaustion, is projected to double by the 2050s and continue to rise.” There is no evidence that this is the case, especially because the climate is COOLING over time because of the current cycle of the Sun, and will be cooling until at least 2050. Hot weather is experienced every year. Separating weather from climate is important. There is no ‘man-made global warming’ …

    1. NONSENSE NON-SCIENCE R.W. DISINFO

      So then people who have lived around the Arctic circle for millennia like the Sami (probably “Laplanders” to you) and the Inuit (“Eskimos”) are liars. And the polar bears aren’t starving, just on diets. The glaciers visibly retreating world-wide are merely remodeling.

      The usual right wing dismissal for the mountains of supporting scientific data is that the scientists are just after grant money. Calling them “global warming industry” as if the U.S. corporate agenda driven university research system gives away scads of $$$ for data that makes them look bad. Not to mention in the rest of the world, scientists don’t have to find sponsors and aren’t for profit. There is not incentive to report anything but confirmed results.

      Your supporting arguments don’t hang together and don’t make your case. You’ve grabbed a decontextualized fact from some right wing source about the current sunspot minimum claiming it means cooling. But there is no evidence for another Maunder Minimum. And if it did mean some solar decrease as Earth temps go up, wouldn’t that be proof of how very much humans are affecting the planet?!

      Scientists and people with a modicum of knowledge are constantly emphasizing the difference between climate and weather! The apologists for econ status quo are the ones who deliberately conflate the two. Like during the 2020 Euro harsh winter or Texas Feb. 2021 when right wing pols touted this as proof climate change, particularly as increased temperatures, is fake.

      “There is no ‘man-made global warming’…” How about, for example, urban heat islands? Are those illusions? As for your incredible unsupported assertion, how about presenting some strong data? Where is the evidence of no change, or better yet, of cooling?!

      Please present sound research and rational arguments that refute the tens of thousands of studies confirming climate change by atmospheric scientists, climatologists, and glaciologists.

      And how about the supporting evidence from geologists, oceanographers, hydrologists, botanists, agronomists, population biologists, ecologists, sociologists, and anthropologists? Explain why these other scientific disciplines are presenting such data.

  2. So much for the IRA, especially with its “poison pills” for fossil fuels, as being a “big step”

  3. David Battisti is ignoring methane, Arctic, Anarctic, and Greenland ice melt, loss of aerosol masking as industry shuts down, eventual off gassing of carbon dioxide from the oceans, and coextinctions. It is annoying to keep reading articles from scientists who aren’t looking at the total picture. We will be lucky to still be alive in 2050.

    1. SCIENTIFIC INFO IN CONTEXT

      He’s not “ignoring” this and scientists ARE “looking at the total picture.” But they have to give evidence from their own specific field of expertise. For example, botanists and agronomists are well aware of how climate change is affecting plants. But that doesn’t make them a source for sound data on atmospheric patterns. Can you imagine the field day the RW deniers would have if scientists were to speak in generalizations?

      If you want an example of what happens when data is taken out of context, look at the first comment and my reply to it.

  4. “How much the economy grows” is based on a capitalistic assumption: only capitalism expects infinite growth on a finite planet.

  5. “even as the world reduces it’s greenhouse gas emissions”? That isn’t happening. Full stop.
    Maybe when climate change kills off enough of humanity that our emissions are perforce reduced and you perverversely reason that we have reduced them by deciding to do nothing.

  6. Even though Americans could afford a/c, the heat is drying up rivers and lakes. Looks like we really need desalination not more nuclear ICBM, F35, warships, etc. The whole planet is struggling with lack of fresh water except Canada, so we probably will buy, steal, confiscate, force, war, or charm those northern cousins.

    Scientists worry that warming oceans are about to release frozen methane which might be devastating.
    Researchers forecast that climate will not be gradual but change exponentially.
    This world went thru extinctions before, it could happen again.

  7. SLOUCHING TOWARDS THE BAY BRIDGE

    I’m sitting in my low income seniors’ apt. two blocks from the I-80 approach to the Bay Bridge, San Francisco. It’s Sat. 8:40 pm PDT; traffic is at a crawl in both directions. This in a region known for its liberalism, eco-consciousness, and good public transportation.

    During the initial COVID shut down when the commuter traffic ceased for months, many of us inner city residents discovered that to our delight, we could breathe! No exhaust to trigger asthma. And as people all over the world found out, wild animals re-appeared and birds could be heard singing.

    What did the clear air and quiet teach us? Nothing. We’re back to the same short-sighted and destructive behavior personally and collectively.

    Three decades ago, I did research on transportation issues for a Seattle mayoralty campaign. Turned out increasing good public transportation decreased traffic, which then made it attractive for others to use cars. Soon back to the same congested traffic.

    Fact is there’s a general inability to change much. Then add to that greater and greater population. It’s nice for upper middle class people to discuss ecological issues in the abstract and maybe cut back on consumption here and there, but it’s rather obviously too little too late. Sigh.

  8. This is obtuse fear mongering for the sake of a byline. You are scaring the children who have become trained to be ok with obesity and see themselves melting into a puddle of fat, cut it out. No mention of incentivizing population reduction, no mention of any need to take action to deal with presumed climate change, just fear and hapless “woe is me.” Article is a big fail.

  9. This writer is very careful not to add “aerosol masking” to the equation. When that inconvenient truth is factored in the hopium bubble ( The faster renewable energy comes online and fossil fuel use is shut down, the better the chances of avoiding that. )quickly bursts.

    Let’s stop trying to pretend this is a “problem”, and simply accept that it is a “predicament”. One that appears to be a part of the human civilization life cycle. Like a child playing with building blocks, no sooner do we accomplish building a thing, we quickly want nothing more than to knock it all down and start over.

  10. I can see the future pipelines from Canada will be for water not tar sands oil! When the draining of the Great Lakes starts I don’t think the end will be far off for them or anyone else!

  11. we are ignoring the facts and hurtling towards our own extinction.
    Business as usual seems to be the only thing that matters to governments, and the results will be disastrous. How can any sane person not see this?
    We are hugely manipulated by governments and the media into thinking that those in power know what they are doing by concentrating on the economy…. Do they realise that we can’t EAT money?
    I’m so glad I have lived in better, more caring times, and sad that our young people will have to suffer unimaginably.

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